Pyrans and their Benzo Derivatives: Structure

Hepworth, John D.; Gabbutt, Christopher D.; Heron, B. Mark

doi:10.1016/b978-008096518-5.00110-6

Cited by 17 publications

(8 citation statements)

References 388 publications

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“…In addition, the IR spectra show weak bands in the 1640-1590 cm -1 region assigned to the ν(C=C) stretching mode of the methylenepyran fragment. [18] Interestingly, the organoiron hydrazones 4-6 are formed stereoselectively as the sterically less hindered (E) isomer (about the N=C double bond), as indicated by the unique set of signals in their 1 H and 13 C NMR spectra (see Exp. Sect.…”

Section: Syntheses and Spectroscopic Characterizationmentioning

confidence: 99%

Dipolar Organoiron Pyranylideneacetaldehyde Hydrazone Complexes: Synthesis, Characterization, Crystal Structure, Linear and Nonlinear Optical Properties

et al. 2006

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Section: Syntheses and Spectroscopic Characterizationmentioning

confidence: 99%

Dipolar Organoiron Pyranylideneacetaldehyde Hydrazone Complexes: Synthesis, Characterization, Crystal Structure, Linear and Nonlinear Optical Properties

et al. 2006

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“…The control of enantio-and diastereoselectivity is applicable to the synthesis of cis-and trans-2,5-disubstituted dihydrofurans and cis-and trans-2,6-disubstituted dihydropyrans [28,29] with control of absolute and relative stereochemistry with readily available, enantioenriched allylic [30,31] and homoallylic alcohols [32,33] (Scheme 2). For example, 1 a and 1 e reacted with alkoxides derived from (R)-1-octen-3-ol and (S)-4-penten-2-ol, respectively, in the presence of catalysts derived from the two enantiomers of L 2 to form the branched allylic ethers 5, 5' and 6, 6' with excellent yields and regio-and diastereoselectivities.…”

Section: Angewandte Chemiementioning

confidence: 99%

Iridium‐Catalyzed Intermolecular Allylic Etherification with Aliphatic Alkoxides: Asymmetric Synthesis of Dihydropyrans and Dihydrofurans

Shu

Hartwig

2004

Angewandte Chemie

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Elimination and racemization limit the synthesis of sterically hindered ethers, [1] such as a-chiral ethers, by the Willamson synthesis. Enantioselective transition-metal-catalyzed allylic substitution [2][3][4][5][6] could be used to prepare these materials from achiral or racemic allylic electrophiles, but intermolecular enantioselective reactions of allylic acetates or carbonates with alkoxides are limited. Enantioselective reactions of phenoxides are well documented, [7][8][9] but no metal catalyzes intermolecular enantioselective allylations of alkoxides with broad scope. [10][11][12][13] Lee and Kim [14] as well as Evans and Leahy [15] demonstrated that zinc and copper alkoxides were more reactive for allylic substitution with achiral palladium and rhodium catalysts than alkali metal alkoxides. The palladium-catalyzed reactions generated achiral ethers, but the rhodium-catalyzed reactions formed branched chiral ethers. Reactions of primary alkoxides with optically active allylic acetates occurred with predominant retention of configuration, but reactions of secondary and tertiary alkoxides were conducted with racemic allylic electrophiles. Because the products from reactions of primary alkoxides can be formed by alkylation of an optically active alcohol, but products from reactions of secondary alkoxides cannot, a catalyst that forms optically active products from hindered alkoxides and allylic carbonates is synthetically valuable. We report herein enantioselective reactions of primary, secondary, and tertiary alkoxides with achiral allylic carbonates to form branched chiral allylic ethers in high yields and with high stereoselectivity in the presence of an iridium catalyst containing a phosphoramidite ligand (Scheme 1). [16][17][18][19][20][21][22] To optimize the conditions for the allylation of aliphatic alkoxides with iridium-phosphoramidite catalysts, we studied the reactions of cinnamyl carbonate with benzyloxides (Table 1). Careful selection of carbonate, alkoxide counterion, and nitrogen substituents in the ligand was essential for high yields. Cinnamyl carbonates with small alkyl groups underwent transesterification in competition with etherification, but tert-butyl cinnamyl carbonate (1 a) provided the

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“…Coumarin and its derivatives show a wide range of biological activities such as antitumoral, anti‐inflammatory, antiviral, Central Nervous System (CNS) active, and antioxidant activities . Some of the coumarin derivatives are known for their anti‐HIV activities and also used in pesticidal preparations ; they have also found applications as photosensitizers and fluorescent and laser dyes . Isothiazole derivatives with pharmacophoric substituents have promising pharmacological activities like 5‐amino‐3‐methyl‐4‐isothiazolecarboxylic acid that displayed remarkable antiviral, anti‐inflammatory, and recently discovered, immunotropic action .…”

Section: Introductionmentioning

confidence: 99%

Facile Synthesis of Novel 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one Derivatives as Potential Anticancer Agents

Ambati

Gudala

Sharma

et al. 2017

Journal of Heterocyclic Chem

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A series of 3-(4-phenylisothiazol-5-yl)-2H-chromen-2-one (6a-l) derivatives has been efficiently synthesized by straightforward sequential reactions. Tandem Vilsmeier Hack reaction/cyclization/bromination/ Suzuki cross-coupling reactions were successfully applied to the preparation of title compounds in goodto-high yields. In the synthetic sequences, 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehydes (2) were found to react with ammonium thiocyanate to yield the corresponding 3-(isothiazol-5-yl)-2H-chromen-2ones (3). These derivatives were brominated with N-bromo succinamide to yield the corresponding regioselective 3-(4-bromoisothiazol-5-yl)-2H-chromen-2-one (4). Finally, compound 4 was treated with various phenyl/pyrazole/7H-pyrrolo[2,3-d]pyrimidinyl boronic acids 5a-l in the presence of K 2 CO 3 and Pd catalyst in dimethylformamide to yield the corresponding title derivatives 6a-l. All the synthesized compounds were characterized by analytical and spectral studies. All the final compounds were screened against different cancer cell lines (A549, PC3, SKOV3, and B16F10), and among these compounds, 6b, 6g, 6h, and 6l displayed moderate cytotoxic activity against the tested cell lines. a IC 50 is defined as the concentration, which results in a 50% decrease in cell number as compared with that of the control cultures in the absence of an inhibitor, and was calculated using the respective regression analysis. The values represent the mean AE SE of three individual observations. Pale orange solid (338 mg), yield: 64%; mp: 289-291°C; IR (KBr) υ max (cm À1 );

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Pyrans and their Benzo Derivatives: Structure

Cited by 17 publications

References 388 publications

Dipolar Organoiron Pyranylideneacetaldehyde Hydrazone Complexes: Synthesis, Characterization, Crystal Structure, Linear and Nonlinear Optical Properties

Dipolar Organoiron Pyranylideneacetaldehyde Hydrazone Complexes: Synthesis, Characterization, Crystal Structure, Linear and Nonlinear Optical Properties

Iridium‐Catalyzed Intermolecular Allylic Etherification with Aliphatic Alkoxides: Asymmetric Synthesis of Dihydropyrans and Dihydrofurans

Facile Synthesis of Novel 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one Derivatives as Potential Anticancer Agents

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